1. Field of the Invention
The present invention relates to a metal mold for producing a synthetic resin molded product in a compression-molding method.
2. Description of the Prior Art
Thermoplastic resin molded products have been used in a wide range including interior parts for cars (for example, door trims and instrument panels), interior and exterior parts for home-use electric appliances, etc., and the injection-molding method and the compression-molding method are known as producing methods for such thermoplastic resin molded products.
Moreover, these molded products are formed as thermoplastic resin molded products without a covering material on their surface or covering-material affixed thermoplastic resin laminated products with a covering material on their surface depending on their purposes and applications.
Conventionally, with respect to a molding method for the thermoplastic resin molded product without a covering material on its surface, the compression-molding, method is widely used, in which melted thermoplastic resin is supplied into the cavity of a metal mold consisting of male and female molds and molding is carried out by clamping the male and female molds. With respect to the compression-molding method for the covering-material affixed thermoplastic resin laminated product with a covering material on its surface, a method which preliminarily provides a covering material between the male and female molds before the melted thermoplastic resin supplying process in the above-mentioned molding method is widely used. (Japanese Laid-Open Patent Publication No. 235613/1989 (Tokukai-hei 1-235613).
With respect to metal molds used for the above-mentioned methods, in the case of the thermoplastic resin molded product without a covering material on its surface, it is proposed that the gap of the sliding portion of the male and female molds at the time of mold-clamping be set in the range of 0.02 mm to 0.1 mm [see Japanese Laid-Open Patent Publication No. 34819/1991 (Tokukai-hei 3-34819)], and in the case of the covering-material affixed thermoplastic resin laminated product with a covering material on its surface, it is also proposed that the above-mentioned gap be set in the range of 0.25 to 3 times the restorable thickness of the covering material [see Japanese Laid-Open Patent Publication No. 34830/1991 (Tokukai-hei 3-34830)].
Here, the restorable thickness of the covering material refers to a thickness of a covering material upon application of a maximum compression, which is defined as follows: after a pressure has been applied onto only a covering material, the covering material is allowed to restore its original thickness before the application of the pressure; thus, this value differs depending on the kinds, thickness, etc. of the covering material.
However, the problem with these methods is that since the gap of the sliding portion of the male and female molds is different between metal molds for producing the thermoplastic resin molded product without a covering material and metal molds for producing the covering-material affixed thermoplastic resin molded product with a covering material, discrete metal molds have to be used for the respective product modes even when those thermoplastic resin molded products based upon the same design are produced.
Under such circumstances, the inventors of the present invention have made efforts to develop a metal mold which eliminates the necessity of using respectively discrete molding devices corresponding to the respective manufacturing processes in the case when a synthetic resin molded product without a covering material on its surface and a covering-material affixed synthetic resin laminated product with a covering material on its surface have the same design, and which makes it possible to easily produce the two types of products using basically the same metal mold; thus, the present invention has been devised.
In other words, the present invention provides
(1) a metal mold for producing a synthetic resin molded product in a compression molding method, which is constituted by a pair of male and female molds that are allowed to mutually slide over the entire contact face, with the outer circumferential face of the male mold and the inner circumferential face of the female mold serving as sliding portions at the time of mold-clamping, characterized in that either the male mold or the female mold or both of the molds is constituted by a mold main body and a sliding member that constitutes a portion of the mold over the entire sliding portions or on a portion thereof, and in that the sliding member is freely removably attached to the mold main body,
(2) the metal mold according to item no. 1, wherein the sliding clearance of the male and female molds at the time of mold-clamping is changed by a replacement of two or more of said sliding members having different sliding clearances between the outer circumferential face of the male mold or the inner circumferential face of the female mold,
(3) the metal mold according to item no. 1 or 2, wherein the synthetic resin is thermoplastic resin,
(4) a molding device which is characterized by comprising the metal mold as defined in item 1, 2 or 3,
(5) a method for producing a synthetic resin molded product, which comprises the step of clamping the metal mold as defined in item 1, 2 or 3,
(6) use of the metal mold as defined in item 1, 2 or 3 for producing a synthetic resin molded product.